[AMPS] Re:

Ian Roberts itr@nanoteq.co.za
Tue, 27 Jul 1999 15:22:10 +0200


With any voltage-measuring device along a transmission line, there is
ambiguity regarding the possibility of placing the probe at a voltage
minimum instead of at a voltage maximum (which is presumably the reading
of interest).

The description of a load SWR of 1 is for legal eagles to ponder over,
not even HP, Rhode and Schwarz, etc., offer such devices in our real
world. For example, if someone's 10 kW linear was impounded by the feds
and measured into a termination with SWR of 1.001, this is not legal
fare if the requirement is for a SWR of 1.

When things become too incomrehensible, people start interpreting the
meaning to suit themselves; a fellow appearing in court with a smart
laywer could rate himself distintly unlucky to have a prosecution stick
against him. Imagine the debate on the "average" power value of "one" RF
cycle?
Ian, 
ZS6BTE

> >>When the FCC measures power, they use a regular peak reading
> >>meter. .....
> >
> >€  wanna guess how such meters are ultimately calibrated?.
> >
> Not against a 'scope, but ultimately against a terminating thermal
> wattmeter which is the only system that is absolute and verifiably
> broadband.
> 
> Scopes and all kinds of "through-line" wattmeters don't actually measure
> power - they measure voltages and/or currents, maybe only proportional
> to the voltages and currents in the line (and the ratios may vary with
> frequency).

> >The definition of PEP does refers to "one cycle" but that means "one or
> >more identical RF cycles" as distinct from "the peak inside a single RF
> >cycle". 
> 
> Sorry, Ian, no because it is a strict definition, applicable in all
> circumstances - such as, for example, broadband ground searching radar.

--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm